The present disclosure relates to a sewing machine that includes a swinging mechanism that is configured to swing a needle bar in the left-right direction.
A sewing machine is known which includes a swinging mechanism that is configured to swing a needle bar between a left needle drop position and a right needle drop position so that the sewing machine can form zigzag stitches. When the needle bar is swung by the swinging mechanism, an outer shuttle rotates at a certain rotation speed. Therefore, corresponding to whether the needle bar is located in the left needle drop position or in the right needle drop position, a timing (an encounter timing) at which a hook point, which is provided on the outer shuttle, catches an upper thread loop is different. Specifically, when the needle bar is located in the right needle drop position, the height of an eye of a sewing needle with respect to the hook point at the encounter timing is lower than that when the needle bar is located in the left needle drop position. As a result, when the needle bar is located in the right needle drop position, the upper thread loop is small. Therefore, it is more likely that the hook point cannot reliably hook and catch the upper thread loop. When zigzag stitches are formed, a known sewing machine rotates the outer shuttle at a non-uniform speed and thereby delays the encounter timing when the needle bar is located in the right needle drop position. Thus, even when the needle bar is located in the right needle drop position, the upper thread loop has a favorable size. Therefore, the hook point can reliably hook and catch the upper thread loop. On the other hand, when straight stitches are formed, normally, the needle bar is located in the left needle drop position. Therefore, there is no need for the sewing machine to rotate the outer shuttle at a non-uniform speed. The above-described known sewing machine includes a dedicated pulse motor that is configured to switch whether or not to rotate the outer shuttle at a non-uniform speed, corresponding to whether straight stitches are formed or zigzag stitches are formed.